NPTN General Fact Sheets are designed to answer questions that are commonly asked by the general
public about pesticides that are regulated by the U.S. Environmental Protection Agency (U.S. EPA).
This document is intended to be helpful to professionals and to the general public for making decisions
about pesticide use.
Pesticides in Indoor Air
of Homes
National
Pesticide
Telecommunications
Network
(General Fact Sheet)
Please refer to the Technical Fact Sheet for more technical information.
The Pesticide Label: Labels provide directions for the proper use of a pesticide product. Be sure to read the entire label before
using any product. A signal word on each product label indicates the product’s potential hazard by ingestion, inhalation, dermal
contact, and eye exposure.
CAUTION - low toxicity
WARNING - moderate toxicity
DANGER - high toxicity
Why might pesticides in indoor air of homes be a concern?
C
Many household products are pesticides, such as lawn and garden products, insect sprays and baits, disinfectants, and rat
poison. Examples of pests that pesticides control include insects, plants, rodents, and microorganisms (1, 2).
C
The acute toxicity of the pesticide product is indicated by a
signal word (Caution, Warning, or Danger). The signal word
reflects the combined toxicity of active and other ingredients.
Subchronic and chronic toxicity such as reproductive,
developmental, and cancer effects may be of concern
depending on the specific active ingredient and the exposure
(route, length, and timing). See boxes on The Pesticide
Label and Cancer.
Cancer: The U.S. EPA has strict guidelines that require
testing of pesticides for their potential to cause cancer.
These studies involve feeding laboratory animals large
daily doses of the pesticide over most of the lifetime of
the animal. Based on these tests, and any other available
information, EPA gives the pesticide a rating for its
potential to cause cancer in humans. For example, if a
pesticide does not cause cancer in animal tests at large
doses, then the EPA considers it unlikely the pesticide
will cause cancer in humans. Testing for cancer is not
done on human subjects.
C
People spend the majority of time indoors, possibly greater
than 90% of their day. The average percent of time spent
indoors at home has been estimated from 60-90% (3).
C
People are exposed to pesticides primarily in the home (3). Approximately 90% of all households in the United States use
pesticides (4). The number and concentration of pesticides detected in indoor air have been shown to be typically greater
than those detected in outdoor air (5).
C
C
People are exposed to pesticides are by inhaling them, accidentally
eating them, and getting them on their skin (6). Inhaling pesticides can
be a major route of exposure (5, 7-11). Note: This fact sheet does not
address indoor exposures other than inhalation nor any routes of
exposures occurring outdoors.
The majority of pesticide exposures in the home as a result of
applications made according to the product labels are at levels below
those anticipated to cause adverse health effects.
Dose-response. The effect of pesticides on
human health depends on how much chemical
is present, the length and frequency of
exposure, and the toxicity of the pesticide.
Effects also depend on the health of a person
when exposure occurs. Laboratories can
detect pesticides in indoor air at extremely low
levels that may not necessarily be harmful to
humans.
How do pesticides get into the indoor air of homes?
C
C
Pesticides enter indoor areas via indoor use and storage, track-in by
people and pets from outdoor areas, or outdoor air entering the home
(12-15). Pesticides may be found indoors even when there is no known
use of pesticides on the property (16).
Once in air, pesticides may exist as gases, liquids, or solids, or as an
aerosol (17).
What are the health risks from pesticides in the
indoor air of homes?
Air Levels. The level of pesticide in air is the
amount of pesticide present in a fixed volume of
air. The amount of pesticide is often
represented in milligrams (mg) or micrograms
(µg) and volume in liters (L) or cubic meters
(m3). Pesticides in air may also be measured in
parts per million (ppm) or billion (ppb). This
means the pesticide occupies one volume for
every million or billion volumes of air (18).
C
The risk with breathing pesticides depends on the toxicity of the
pesticide and the level of exposure. See boxes on Dose-response, Air
Levels, and Breathing Rate.
C
When breathing pesticides, the respiratory tract is the first organ
system that pesticides contact. This system extends from the nose and
mouth to the lungs (20). The respiratory system is important in
distributing inhaled pesticides (21).
C
Breathing pesticides may affect multiple organ systems or just the respiratory system (21).
C
An individual’s health status affects his/her response to inhaled pesticides (22). Individuals with preexisting health
conditions or impaired health status, particularly respiratory diseases, may be more susceptible to inhaled pesticides.
Breathing Rate. Breathing rate is the amount
of air inhaled per time. A person’s age, gender,
weight, health status, and activity level
(sleeping, walking, running, etc.) affect
breathing rates. Higher breathing rates
increase the exposure to pesticides in indoor
air and may translate into greater risk (19).
What factors influence the level and fate of pesticides in the indoor air of homes?
C
The pesticide level in indoor air is determined by the amount of pesticide in the home and how fast the pesticide leaves
the air by venting outdoors, degradation, or settling to the ground (23).
C
The volatility of a pesticide affects the level of pesticides in air
(24). Temperature, humidity, and formulation type influence
the volatility of a pesticide (5, 24-26). See box on Volatility.
Volatility. Volatility is the tendency of a pesticide to
convert a liquid or solid into a gas. The greater the
volatility of a pesticide, the more likely the substance
will be present as a gas.
C
Different application methods may result in different levels of pesticides in air (9, 27, 28). The frequency of application
also influences air levels.
C
Seasonal changes cause variations in the presence and levels of pesticides indoors. The season influences pesticide use
and changes in the heating, cooling, or ventilation of air. Seasons also influence people’s activity levels (5).
C
Building characteristics impact indoor pesticide air levels (23). Exhaust fans and heating and air conditioning systems
influence air movement within the home and the exchange of indoor air with outdoor air (“leakiness” of the home) (23).
C
People and pets track-in and distribute pesticides indoors from pesticide-treated lawns (12, 13). Indoor activities such as
walking in a pesticide-treated area or vacuuming can temporally increase pesticide levels in air (23, 29).
C
Pesticides distribute in indoor air from indoor or outdoor sources. Levels of pesticides in indoor air may vary within a
room and between rooms (7, 14, 30-32).
C
Pesticides in the air settle out onto surfaces. Once they are on the surface, the pesticide may stay there or be resuspended
in air (7, 9-11, 23, 25, 28, 32, 33).
C
Pesticides may degrade indoors. Faster degradation rates
typically result in lower air levels and less persistence of
pesticides in air (24). Degradation rates for pesticides indoors
may be slower than outdoor rates, resulting in prolonged
presence indoors (34). The degradation rate is often represented
as a half-life. See the box on Half-life.
C
Opening windows and using fans to ventilate the area reduces
indoor air levels of pesticides (9-11, 24, 25, 32, 35).
Researchers suggest that indoor pesticide air levels may depend
on ventilation (10, 11).
Half-life is the time required for half of the compound
to degrade.
1 half-life
2 half-lives
3 half-lives
4 half-lives
5 half-lives
=
=
=
=
=
50% degraded
75% degraded
88% degraded
94% degraded
97% degraded
Remember that the amount of chemical remaining
after a half-life will always depend on the amount of
the chemical originally applied.
What is the risk when I smell pesticides inside
my house?
C
An odor is evidence of exposure to a pesticide in air, but it is not necessarily evidence of toxicity (28). The odor can be
unpleasant and it may cause nasal irritation, nausea, or headaches (28, 36).
C
Odor from a pesticide may be caused by one or several chemicals contained in a pesticide. Detecting an odor depends on
the level of pesticide present in air and an individual’s odor threshold (lowest level that you can smell a chemical) (28).
How can I minimize exposure to pesticides in indoor air of my home?
C
If possible, use nonchemical pest control methods such as good home hygiene, sealing entry points for pests and removing
sources of food and water (37).
C
If the pesticides are coming from outdoor sources, minimize the outside air getting inside. Close windows and shut off
mechanical systems that ventilate with outdoor air. Open the windows when spraying indoors.
C
To minimize pesticide track-in from outdoor treated areas, remove your shoes before you enter the home or use an outdoor
shoe cleaning device prior to entering the home, and limit pet access to treated areas (12).
C
Store pesticides in the original containers in secure sites outside of areas where people and animals spend large amounts
of time. Keep pesticides in locations not accessible to children.
C
Read the label and follow directions. Adverse health effects are not expected from pesticides used in accordance with the
label. Use pesticides only in ways consistent with the label directions (37).
C
Treat indoor plants and animals outside whenever possible. Mix or dilute pesticides outside or in well-ventilated areas
(37).
C
If you use pesticides to treat an indoor area, ventilate the area. If listed, follow the pesticide label for ventilating and
reentering treated areas (37).
C
Call the National Pesticide Telecommunications Network (NPTN) at 1-800-858-PEST (7378) for more information.
Date reviewed: February 22, 2001
For more information contact: NPTN
Oregon State University, 333 Weniger Hall, Corvallis, Oregon 97331-6502.
Phone: 1-800-858-7378 Fax: 1-541-737-0761 Email: nptn@ace.orst.edu
NPTN at http://nptn.orst.edu/ EXTOXNET at http://ace.orst.edu/info/extoxnet/
Or:
U.S. EPA Indoor Air Quality Information Clearinghouse
IAQ INFO
P.O. Box 37133, Washington, DC 20013-7133
Copies of this factsheet are not available at this hotline.
Phone: 1-800-438-4318
Fax: 1-703-356-5386
Email: iaqinfo@aol.com
U.S. EPA Indoor Environments Division at http://www.epa.gov/iaq/
References
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NPTN is sponsored cooperatively by Oregon State University and the U.S. Environmental Protection Agency. Data presented through NPTN
documents are based on selected authoritative and peer-reviewed literature. The information in this profile does not in any way replace or supersede
the restrictions, precautions, directions or other information on the pesticide label/ing or other regulatory requirements.